[adhrp]

Originally Posted by Drifttime85

They did the pressure test and said no leaks like you said. Do you know of something I can request additionally that I can pay out of pocket ? I don’t want to run into a bigger issue out of warranty.

One thing perhaps you can do is ask them to look at the underside of the engine after the pressure test is applied since the few drops of leaking coolant might show up somewhere. But again that could be concealed depending on where the leak is. I'm guessing they'll be happy to dig into the engine if you pay them but that can get costly quickly. A good SA will probably dissuade you from doing that. My SA even dissuaded me from changing other coolant hoses seeing as I was determined to do so after paying 1000 bucks in labor for a $100 part because he said there's just no way to know a hose is leaky until it leaks so I'd be wasting money.

[NateM15]

Your issue is right in your photo, and I say this from my own experience. If you look at the base of the cap, you will see the "crust". That's your leak. It's the small O ring on the underside of the cap that is leaking.

Again. My own 23 m550 is doing the same thing. I have 7500 miles on it.

The solution so far, a VERY slight trace of super lube on all of the O rings on the underside of he cap.

Take a small brush, clean all that crust off at the base of the fill neck and check it in 3 to 4 weeks. You'll see what I'm referring too. My dealer offered to replace the cap on mine and I'm not willing to take a 30 mine drive for that, so it will wait until the next service.

The other dead giveaway, the coolant cryatalizes in the caps threads making it super tough to remove.

Good luck, post back what you find.

Originally Posted by sam555

So I got the dreaded low coolant warning on my 2020 M550 after starting cold after about 4 days.

Car has about 42K miles. I've read all the stuff online about potential coolant issues. My turbo lines etc. are metal, and there doesnt seem to be any leak there on visual inspection.

There was however some white, crusty stuff on top of the coolant tank, and when I opened the cap, a lot of that on top. Attached is a pic.

My question is as follows. My CPO expires in Sept 2024. I understand CPO doesn't cover hoses, but would it cover it in this case? Would CPO cover any other problems - such as cracks etc in the coolant tank? I am hoping mine is an instance of just a bad fitting cap, since so much seems on top!

I dont want the dealer blowing me off with the usual these cars burn coolant etc. I would like them to take a serious look and do whatever needs to be done and replace necessary parts, hopefully under CPO. How do I ensure they do it? What do I tell them etc? Any advise would be appreciated.

Thank you in advance as always!

[jcal65]

Just hit 12k miles and got a low coolant warning this morning on my way to work. No warning on the way home. No visible leaks or coolant smell, engine compartment still looks brand new. I made an appointment for Friday anyway to have the dealer to check it out.

[M550Ali]

Expansion tank going out, take to dealer immediately to prevent leaking into places you don’t want coolant going (I’m no mechanic but it happened to me 2020 m550i)

[NGT2]

Originally Posted by Joe-BMW33

You are exactly right. You should not be adding coolant in an 8 month old car. Think about, have you EVER had to do this for any other car in your history?

I’ve never had a low coolant warning on any car until my 540 and 550.

[NGT2]

Originally Posted by Drifttime85

They did the pressure test and said no leaks like you said. Do you know of something I can request additionally that I can pay out of pocket ? I don’t want to run into a bigger issue out of warranty.

Honestly, I think if it’s leaking then it’s very slow. And I think it will eventually give you another warning. Mine tended to happen when I hadn’t driven in a day or two. And all three times (if you include the 540) it turned off before I got to the dealer. I think the coolant heats up and expands and hits the mark. But the warning should never come on. I’d just be diligent about it and when it comes on again, be sure and point out that it’s the second time in X months and it’s a pretty new car.

Or it won’t come on again for years and they will have been right!

I just would be concerned if this happens like 3-4 times in 12-18 months time and they keep going with evaporation.

Basically, I’d just do what I actually did do. Let them be the experts and when it happened again, I made sure and pointed out it was the second time and they indeed found a leak that time around.

I’ll say for my SA, to his credit, he never blew it off. The first time he gave it a once over and didn’t see anything so he said “let’s top it off and this will be our benchmark and if it happens again, we’ll assume there’s a leak somewhere we can’t see.” I thought that was fair enough. Having the support of the warranty helped, too.

[NGT2]

Originally Posted by NateM15

Your issue is right in your photo, and I say this from my own experience. If you look at the base of the cap, you will see the "crust". That's your leak. It's the small O ring on the underside of the cap that is leaking.

Again. My own 23 m550 is doing the same thing. I have 7500 miles on it.

The solution so far, a VERY slight trace of super lube on all of the O rings on the underside of he cap.

Take a small brush, clean all that crust off at the base of the fill neck and check it in 3 to 4 weeks. You'll see what I'm referring too. My dealer offered to replace the cap on mine and I'm not willing to take a 30 mine drive for that, so it will wait until the next service.

The other dead giveaway, the coolant cryatalizes in the caps threads making it super tough to remove.

Good luck, post back what you find.

This tracks with others I’ve read in the past. Seems the whole system is vulnerable. The caps, the hoses, and the tank itself.

[NGT2]

And I’m guessing the engineers and QC people would love to fix it. I’d venture to guess it’s the accountants that want to leave it be. Which makes sense on a model they aren’t selling anymore. And the only group that will overpower the bean counters is the lawyers. Which apparently they finally did on the M5 and M8 because they have a stop sale over their leaky tanks.

[adhrp]

Originally Posted by NGT2

Honestly, I think if it’s leaking then it’s very slow. And I think it will eventually give you another warning. Mine tended to happen when I hadn’t driven in a day or two. And all three times (if you include the 540) it turned off before I got to the dealer. I think the coolant heats up and expands and hits the mark. But the warning should never come on. I’d just be diligent about it and when it comes on again, be sure and point out that it’s the second time in X months and it’s a pretty new car.

Or it won’t come on again for years and they will have been right!

I just would be concerned if this happens like 3-4 times in 12-18 months time and they keep going with evaporation.

Basically, I’d just do what I actually did do. Let them be the experts and when it happened again, I made sure and pointed out it was the second time and they indeed found a leak that time around.

I’ll say for my SA, to his credit, he never blew it off. The first time he gave it a once over and didn’t see anything so he said “let’s top it off and this will be our benchmark and if it happens again, we’ll assume there’s a leak somewhere we can’t see.” I thought that was fair enough. Having the support of the warranty helped, too.

My recent leak was so slow that I would have been fine topping it off every 2-3 months until it got worse, and $1200 would have bought a lot of coolant! But two things bothered me - 1) I didn't want coolant collecting or searing on other parts of my engine and 2) there's a TSB for this exact hose for the B48 for certain model years, and given how important this hose is, I didn't want to wait for a catastrophic failure (see this thread: https://f30.bimmerpost.com/forums/sh....php?t=1889354). I think most folks with "invisible" slow leaks will be fine topping it off until it worsens i.e. becomes visible.

[sam555]

Originally Posted by NateM15

Your issue is right in your photo, and I say this from my own experience. If you look at the base of the cap, you will see the "crust". That's your leak. It's the small O ring on the underside of the cap that is leaking.

Again. My own 23 m550 is doing the same thing. I have 7500 miles on it.

The solution so far, a VERY slight trace of super lube on all of the O rings on the underside of he cap.

Take a small brush, clean all that crust off at the base of the fill neck and check it in 3 to 4 weeks. You'll see what I'm referring too. My dealer offered to replace the cap on mine and I'm not willing to take a 30 mine drive for that, so it will wait until the next service.

The other dead giveaway, the coolant cryatalizes in the caps threads making it super tough to remove.

Good luck, post back what you find.

Wow...this literally sounds like whtas happening to my car. The coolant cap was an enormous pain to twist off and was immensely tight. I will give it a clean and take another look as you suggested. The cap is $25 if I am not mistaken, and hope thats all it is.

[jcal65]

I took my car to the dealer this morning to address a low coolant warning. After a pressure test, it was determined the water pump was leaking, a new one has been ordered. Only got 12k miles out of the original pump.

[sam555]

So I popped the hood today to find this. Coolant splashed all over...the cap area in particular looks bad. The cap itself was wet with coolant when I unscrewed it after it cooled down. I am hoping the cap is the main culprit. Ordered one from Advanced Auto Parts as he said he would be getting it to me by tomorrow morning. Will try it on and see if it solves the problem. Hopefully it does....

[NateM15]

Originally Posted by sam555

Wow...this literally sounds like whtas happening to my car. The coolant cap was an enormous pain to twist off and was immensely tight. I will give it a clean and take another look as you suggested. The cap is $25 if I am not mistaken, and hope thats all it is.

Yup. It took me about 15 minutes of Tightening and loosening the cap back-and-forth, to get it free. I thought it was just on incredibly tight, and of course this first happened at like 4500 miles so I was shocked it was on so tight. But after getting it off completely and looking at the crystallized coolant in the threads, I knew exactly what happened.
---
Right or wrong, I'm not going to lie to not say that some of that super lube grease didn't make it on to the threads of the reservoir and the underside threads of the cap as well.

My first warning and encounter of this issue happened at home so I had the strap wrench and time to fiddle with it and break it free.

The last thing I want is to get a low coolant warning 100 miles from home and no way to get the GD cap off. Coating the threads makes sure that won't happen.

[tsbrown]

Originally Posted by NateM15

Your issue is right in your photo, and I say this from my own experience. If you look at the base of the cap, you will see the "crust". That's your leak. It's the small O ring on the underside of the cap that is leaking.

Again. My own 23 m550 is doing the same thing. I have 7500 miles on it.

The solution so far, a VERY slight trace of super lube on all of the O rings on the underside of he cap.

Take a small brush, clean all that crust off at the base of the fill neck and check it in 3 to 4 weeks. You'll see what I'm referring too. My dealer offered to replace the cap on mine and I'm not willing to take a 30 mine drive for that, so it will wait until the next service.

The other dead giveaway, the coolant cryatalizes in the caps threads making it super tough to remove.

Good luck, post back what you find.

So is this the only sign? I’ve had 2 low coolant warnings in 5 years on my car and before I take my 1000 mile drive north I want to ensure I won’t get another. Looking around both tanks and hoses there are no obvious leaks. However there is some crustiness around the caps. Should I just replace the caps preemptively?

[HerkHealer]

Here's a pic of my reservoir cap that failed.
Got a new one from the dealership, which they had in stock for about $25 IIRC.
I had to use a large set of channel locks to get the cap off. It was frozen from the dried up coolant.
Problem solved.

[NateM15]

Originally Posted by tsbrown

So is this the only sign? I’ve had 2 low coolant warnings in 5 years on my car and before I take my 1000 mile drive north I want to ensure I won’t get another. Looking around both tanks and hoses there are no obvious leaks. However there is some crustiness around the caps. Should I just replace the caps preemptively?

I don't see replacing the cap as a "rush" type item as I know what it is and what the problem consists of and how to solve it.

My dealer said they would replace it at the next service interval if I wanted it done. Of course they would not say " we've seen this before" but I got the vibe based on their conversation that they know it's a known issue.

But since I used the lube on the O rings and on the threads of the cap and Reservoir neck I have not seen an issue. So I'm content to leave it at that.
Attached is a photo of what I used. They make an "O ring" version as well but this is available at pretty much any hardware store. And like I said previously I only used a slight trace on it, not gobs of it that is going to drip down into the coolant.

I cleaned up the top of the fill neck on the bottle and it the neck base. I pop the hood periodically to see if there is any residue there, but since the lube addition it's been almost nonexistent.

[Joe-BMW33]

Originally Posted by NateM15

Yup. It took me about 15 minutes of Tightening and loosening the cap back-and-forth, to get it free. I thought it was just on incredibly tight, and of course this first happened at like 4500 miles so I was shocked it was on so tight. But after getting it off completely and looking at the crystallized coolant in the threads, I knew exactly what happened.
---
Right or wrong, I'm not going to lie to not say that some of that super lube grease didn't make it on to the threads of the reservoir and the underside threads of the cap as well.

My first warning and encounter of this issue happened at home so I had the strap wrench and time to fiddle with it and break it free.

The last thing I want is to get a low coolant warning 100 miles from home and no way to get the GD cap off. Coating the threads makes sure that won't happen.

I did the same thing in terms of greasing the threads a little. A few months after I got my car I got the low coolant warning (which turned out to be the turbo lines leaking) and I went to take this cap off. Had to use the channel locks if was so tight. Got it off and had the same crusty mess. I cleaned it and lubed up the thread. I can't remember what I used. Some form of petroleum lube. Problem solved, although I have not had to take that cap off for over two years now.

[tsbrown]

It took channel locks to get my cap off and the coolant was down to min so I'm off to the dealer to get a new cap and coolant to mix. Will pick up some of this lube for the threads on the way. Hopefully that will solve the issue, at least in the near term.

[tsbrown]

Went out looking for Super Lube and couldn't find it in a local store but there are other options. Just be careful not to pick something that has additives that can prematurely degrade the plastic (Esters and polyglycols, graphite and molybdenum). That's where Super Lube is good. Their compatibility sheet lists either Excellent or Good compatibility with most plastics. There's one other place nearby that should have it and will try that tomorrow.

[sam555]

Thanks to NateM15 and HerkHealer . My cap area was looking very similar. Happy to report that I replaced it and see no tell tale signs for the last two days of any leaking coolant on top. The cap I used was a CarQuest cap from Advance Auto. For whatveer reason it is a much more snug fit than the original. The original cap has this slight bit extra space in front and looks a lot like HerkHealer 's pic. With the CarQuest cap that is not there. Keeping fingers crossed and hope this solves the problem...

[abr0wne]

My radiator had a leak, it was replaced. I was still getting coolant warning, come find out the sensor was defected, but it’s in the dispenser tank. Therefore, dispenser tank was replaced about 6 weeks ago, no issues since then.

[Neusser]

Originally Posted by NateM15

I don't see replacing the cap as a "rush" type item as I know what it is and what the problem consists of and how to solve it.

My dealer said they would replace it at the next service interval if I wanted it done. Of course they would not say " we've seen this before" but I got the vibe based on their conversation that they know it's a known issue.

But since I used the lube on the O rings and on the threads of the cap and Reservoir neck I have not seen an issue. So I'm content to leave it at that.
Attached is a photo of what I used. They make an "O ring" version as well but this is available at pretty much any hardware store. And like I said previously I only used a slight trace on it, not gobs of it that is going to drip down into the coolant.

I cleaned up the top of the fill neck on the bottle and it the neck base. I pop the hood periodically to see if there is any residue there, but since the lube addition it's been almost nonexistent.

Yep, the fix is that simple if the cap is leaking.

I had a very slow leak that seems to have gone away entirely after lubing the threads on the old cap.

I just used some old Shimano bike lube I had lying around. It's clearly an issue with hard heat-cycled plastic that is causing pressure loss.

New cap is not needed. I also removed my engine cover and may remove the foam insulation. I think the encapsulation of the engine causes the plastics to break down much faster than they should.